EP1404554B1 - System for controlling driving dynamics - Google Patents

Abstract

The performance of a system for controlling vehicle-movement dynamics, which operates the braking system and the drive train of a vehicle in order to prevent lateral breakaway of the vehicle, is improved yet further for the case in which oversteering of the vehicle is to be compensated. To this end it is proposed, according to the invention, that a braking moment be produced on the front wheel on the outside of the bend by the braking system, and an additional drive moment be built up by the drive train on the driven wheels.

Description

The invention relates to a system for vehicle dynamics control, which acts via the braking system and the drive train of a vehicle to prevent lateral breaking of the vehicle.

A Vehicle Dynamics Control (FDR) system significantly improves driving safety through the advantages of the anti-lock braking system (ABS), which prevents wheel locking when braking, and traction control (ASR), which avoids wheel spin when driving Driver actively supported in lateral dynamic critical situations. As is known, the vehicle dynamics control system acts in the brake system to actively restore driving stability in the event of under- or oversteering driving behavior by braking of individual wheels that is independent of the driver. For example, the rear wheel on the inside of the curve is actively decelerated when understeering and the front wheel on the outside of the curve is actively braked when oversteering. It is also known that the vehicle dynamics control engages in the drive train to reduce by withdrawing the engine torque, the drive torque or the traction on the driven wheels, when driving front-wheel drive understeer or in rear-wheel drive vehicles to counteract oversteer.

The EP-A-0 842 836 describes a system for vehicle dynamics control. During braking, a drive force is generated based on a braking force, which at least partially compensates for the braking force. Thereby, a vehicle can be controlled from a current vehicle movement to a destination movement that corresponds to the steering direction. By means of this control system, when the vehicle brake pedal is actuated by a vehicle driver, adequate braking of the vehicle can be achieved while vehicle stability is maintained.

The object of the invention has been set to design an aforementioned system for vehicle dynamics control even more efficient in the event that an oversteer of the vehicle is to be compensated.

To solve the problem it is proposed that to prevent oversteer of the vehicle over the Braking system on the outside of the curve outside a braking torque is generated and via the drive train to the driven wheels an additional drive torque is built up. First, the additional drive torque is built up on the driven wheels, and only when the oversteer of the vehicle does not decrease after a predetermined period of time, the braking torque is generated at the curve outer front wheel. It is therefore a certain period of time to wait, whether the driving behavior stabilized solely due to the built-up on the driven wheels additional drive torque.

In principle, the generation of the braking torque on the outer curve-side front wheel and the build-up of the additional drive torque on the driven wheels could take place simultaneously.

The great advantage of the invention is that the additional drive torque generates a further component which counteracts the yawing motion of the vehicle when oversteer. It is of significant advantage in this case that the additional component generated by the additional drive torque acts on a different wheel of the vehicle than the curve outer front wheel loaded with the braking torque. As a result, the counter torques for intercepting the yaw motion of the vehicle during oversteer are shifted to several wheels. Overall, this results in both a safety gain, as the system performance increases, as well as a gain in comfort, as the control process is more harmonious and thus less reactive for the driver.

There is also no risk that too high a slip occurs due to the additionally constructed drive torque at one or more driven wheels, which would adversely affect traction and vehicle stability again. Because the vehicle dynamics control builds on the traction control system and also uses their already existing components, one of the vehicle dynamics control can intervene depending on the system design over or subordinate traction control if due to the additionally constructed drive torque of the slip on one or more driven wheels exceeds a predetermined value.

In order not to disturb the harmonic control process by the load change reactions perceptible to the driver, the braking torque generated on the outer curve of the curve is only built up when the additional drive torque at the driven wheels has reached a predetermined value.

Preferably, the braking torque generated on the curve-outer front wheel is of the order of magnitude twice as large as the drive torque previously additionally built up on a driven wheel.

The inventive system is equally applicable for vehicles with front or rear or all-wheel drive.

In particular, in vehicles with all-wheel drive need not be switched to driving dynamics control by switching the center differential to front-wheel drive, so that the benefits of the inventive system particularly come to fruition because for four-wheel drive in principle implemented for front and rear wheel drive control operations can be superimposed.

In particular, when the additional drive torque is built up on the rear wheels, which is the case in a vehicle with rear or all-wheel drive, an additional braking torque can be generated on the curve outer rear wheel. As a result, the drive torque additionally built up on the outer rear wheel is compensated for, so that the rear wheel on the inside of the curve additionally built-drive torque supports the braking torque generated at the outer curve front even more to counteract the yawing motion of the vehicle when oversteer.

In order to completely compensate for the drive torque which is additionally built up on the curve-outer rear wheel, the braking torque additionally generated on the curve-outer rear wheel is set to the same magnitude as the drive torque previously built up on the inside rear wheel.

If it is to be awaited whether the driving behavior stabilizes without generating the additional braking torque on the curve outer rear wheel, the additional braking torque on the curve outer rear wheel can only be generated if oversteering of the vehicle does not decrease after a predetermined period of time.

In order to avoid noticeable to the driver load change reactions, there is the possibility that the additional braking torque is generated at the curve outer rear wheel only when the drive torque generated at the curve outer rear wheel has reached a predetermined value.

Fig. 1

das Ausführungsbeispiel für ein frontgetriebenes,

Fig. 2

das Ausführungsbeispiel für ein heckgetriebenes,

Fig. 3

das Ausführungsbeispiel für ein allradgetriebenes Fahrzeug.

The invention and its further features will be explained in more detail with reference to an embodiment with drawing. In addition shows

Fig. 1

the embodiment of a front-wheel drive,

Fig. 2

the embodiment of a rear-drive,

Fig. 3

the embodiment of a four-wheel drive Vehicle.

The schematically illustrated vehicle 1 is in Fig. 1 to 3 each identical. The vehicle 1 has a left and a right steerable front wheel 2, 3 and a left and right rear wheel 4, 5. The forward movement of the vehicle 1 takes place in the direction of travel X, wherein the steerable front wheels 2, 3 are turned to the left, so that the vehicle 1 drives a left turn for the embodiment. In this case, the rear of the vehicle 1 breaks when oversteer sideways to the right, so that the vehicle 1 a smaller radius of curvature than he corresponds to the steering angle of the front wheels 2, 3, drives.

In a vehicle dynamics control, among other things, the yaw moment M _{yawl of} the vehicle 1 about its vertical axis 6 and the steering angle predetermined by the driver or steering angle of the front wheels 2, 3 are detected and evaluated in order to detect oversteer at an early stage. If an oversteer is detected, a brake torque M _{BRAKE is set} up via the brake system on the curve outer front wheel, which _counteracts the yaw moment M _{GIER of} the vehicle 1 about its vertical axis 6 in order to stabilize the vehicle _behavior .

Since the vehicle 1 runs a left-hand _{bend in the exemplary embodiment,} a braking torque M _{BRAKE, VR is} built on the right-hand front wheel 3.

According to the invention, in addition to the braking torque M _BRAKE , a drive torque M _{DRIVE is built up} on the driven wheels on the outer wheel outside the curve. How this is done with the different drive types is explained below.

Fig. 1 - front-wheel drive

In a front-wheel drive vehicle, a drive torque M _{DRIVE, VL} , and on the right front wheel 3, a drive torque M _{DRIVE, VR is} additionally generated on the left front wheel 2. Although at the right front wheel 3, the braking torque M _{BRAKE, VR weakened} by the additional drive torque M _{DRIVE, VR} in a "certain mass", however, is generated by the additional drive torque M _{DRIVE, VL} on the left front wheel 2, a further component that the _Yaw moment M _{yaw of} the vehicle 1 counteracts about its vertical axis 6.

Preferably, an additional total drive torque M _DRIVE , _{TOTAL is set} up on the driven front wheels 2, 3, which corresponds to the brake torque M _{BRAKE, VR} set on the outer wheel 3 on the outside of the curve, that is M _{DRIVE, TOTAL} = M _{BRAKE, vR} . The total _{drive torque} M _{DRIVE, TOTAL} distributed in equal parts to the driven front wheels 2, 3, so that for the wheel drive _torque M _{DRIVE, VL} = M _{DRIVE, VR} = ½ M _{BRAKE, VR} applies. Consequently, the braking torque M _BRAKE is at the kurvenäusseren front wheel 3 _is reduced by half _VR by the additional drive moment M _{DRIVE, VR.} Since an additional drive torque M _{DRIVE, VL} is available parallel to the curve- _inward front wheel 2, which corresponds to the reduction of the braking torque M _{BRAKE, VR} on the curve-outside front wheel 3, the moment _balance overall behaves at least neutral to the yaw moment M _{yawl of} the vehicle 1 to counteract its vertical axis 6. Although not necessarily a higher Gegengiermoment is generated, it is essential for the invention that the yaw moment M _{yaw of} the vehicle 1 when oversteer equally over both Front wheels 2,3 is intercepted instead of only on the outside of the curve 3 front wheel. As a result, not only the driving stability is restored faster, but the control process is more harmonious overall.

Fig. 2 - rear-wheel drive

In a rear-wheel drive vehicle, a drive torque M _{DRIVE, HL} and at the right rear wheel 5, a drive torque M _{DRIVE, HR is} additionally generated on the left rear wheel 4. Due to the additional drive torque M _{DRIVE, HL} on the left rear wheel 4, a further component is generated, which _counteracts the yaw moment M _{yawl of} the vehicle 1 about its vertical axis 6. In this case, the drive torque M _{DRIVE, HR} generated at the right rear wheel 5 weakens the further component generated by the additional drive torque M _{DRIVE, HL} on the left rear wheel 4 in a "certain mass". To counteract this, the drive torque M _{DRIVE, HR} generated at the right rear wheel 5 can at least be compensated, in which an additional braking torque M _{BRAKE, HR is} built up on the right rear wheel 5, so that drive torque M _{DRIVE, HL} generated at the left rear wheel 4 the yaw moment M _{yaw of} the vehicle 1 counteracts about its vertical axis 6 even stronger.

Preferably, an additional total drive torque M _{DRIVE, TOTAL is} constructed on the driven rear wheels 4, 5, which corresponds to the set on the outside of the curve front wheel 3 braking torque M _{BRAKE, VR} , ie M _{DRIVE, TOTAL} = M _{BRAKE, VR} is. The total _{drive torque} M _{DRIVE, GEAMT} distributed in equal parts on the driven rear wheels 4, 5, so that for the wheel drive _torque M _{DRIVE, HL} = M _{DRIVE, HR} = ½ M _{BRAKE, VR} applies. Around To compensate for the drive torque M _{DRIVE, HR} generated at the curve outer rear wheel 5, an additional braking torque M _{BRAKE, HR} is preferably constructed on the curve outer rear wheel 5, which corresponds to half of the adjusted braking torque M _{BPEMS, VR} , ie M _{BRAKE, HR} = M _{DRIVE, HR} = ½ M _{BRAKE, VR} . As a result, an additional counter-yawing moment is made available by the drive torque M _{DRIVE, HL} generated at the inside rear wheel 4. Essential for the invention, however, is that the yaw moment M _{yawl of} the vehicle 1 when oversteer over both rear wheels 4, 5 or at least the inside rear wheel 4 and the curve outer front wheel 3 is intercepted instead of only on the outside wheel 3, so that the overall control process more harmonious and the driving stability is restored faster.

Fig. 3 - four-wheel drive

In a _four -wheel drive vehicle, a drive torque M _{DRIVE, VL} ) on the left front wheel 2, a drive torque M _{DRIVE, VR} ) on the right front wheel 3, a drive torque M _{DRIVE, HL} on the left rear wheel 4, and a drive torque on the right rear wheel 5 M _{DRIVE, HR} additionally generated. The additional drive torques M _{DRIVE, VL} , M _{DRIVE, HL} on the left front and rear _wheels 2, 4 additional components are generated, which _counteract the yaw moment M _{yawl of} the vehicle 1 about its vertical axis 6. Again, the additional drive torque M _{AHTRIEB, VR} , M _{DRIVE, HR} on the right front and rear _wheels 3, 5 weaken the counter components in a "certain mass". In order to compensate for this at least, an additional braking torque M _{BRAKE, VR} can also be built up here on the right-hand rear wheel 5.

Overall, in a vehicle with all-wheel drive, the control processes are superimposed on the front and rear wheel drive. As a result, the yaw moment M _{CIER of} the vehicle 1 when oversteering over both front wheels 2, 3 and both rear wheels 4, 5 or at least the inside rear wheel 4 is intercepted instead of only on the outside front wheel 3, so that a harmonious control process results and the driving stability is restored more quickly becomes.

In connection with the explanation of Fig. 1 to 3 it is mentioned that a weakening of the drive torque (s) can take place in a "certain measure". This measure is essentially determined by vehicle parameters in the stationary and dynamic state, such as track width, center distance, steering angle, center of gravity and axle load distribution, as well as external influences, such as the nature of the road surface.

How the braking torque additionally generated at the outside of the curve wheel and the drive torque additionally built up on the driven wheels are adjusted both in terms of order of magnitude and progressively (eg jump-shaped or ramp-shaped) is determined from the deviation of the driver's steering angle from the actual yawing motion of the driver Vehicle around its vertical axis, whereby the time derivatives (yaw rate) of this deviation are used. In addition, the aforementioned vehicle parameters are considered in the stationary and dynamic state.

Although in the embodiment, the driving of a left turn is considered, so anyway one It will be readily understood by those skilled in the art how the invention works when driving a right turn, with the rear of the vehicle breaking sideways to the left when oversteer and braking torque initially being established on the left front wheel to stabilize driveability.

Claims (7)

1. System for controlling vehicle-movement dynamics, which operates by means of the braking system and the drive train (6) of a vehicle (1) in order to prevent lateral breakaway of the vehicle (1), wherein a braking moment (M_BRAKE,FR) is produced, by means of the braking system, on the front wheel (3) on the outside of the bend, and an additional drive moment (M_DRIVE,_FR, M_DRIVE,FL, M_DRIVE,RR, M_DRIVE,RL) is built up, by means of the drive train (6), on the driven wheels (2, 3, 4, 5), for the purpose of preventing oversteering of the vehicle (1), and wherein a higher-order or lower-order drive-slip control comes into action if the slip on one or more driven wheels (2, 3, 4, 5) exceeds a predetermined value due to the additionally built-up drive moment (M_DRIVE,FR, M_DRNE,FL, M_DRIVE,RR, M_DRIVE,RL), characterized in that the additional drive moment (M_DRIVE,FR, M_DRIVE,FL, M_DRIVE,RR, M_DRIVE,RL) is first built up on the driven wheels (2, 3, 4, 5), and the braking moment (M_BRAKE,FR) is produced on the front wheel (3) on the outside of the bend only if the oversteer of the vehicle (1) does not decrease after a predetermined period of time.
2. System according to claim 1, characterized in that the braking moment (M_BRA-KE,FR) produced on the front wheel (3) on the outside of the bend is built up only if the additional drive moment (M_DRIVE,FR, M_DRIVE,FL, M_DRIVE,RR, M_DRNE,RL) on the driven wheels (2, 3, 4, 5) has attained a predetermined value.
3. System according to claim 1 or 2, characterized in that the braking moment (M_BRAKE,FR) produced on the front wheel (3) on the outside of the bend is of an order of magnitude which is double that of the drive moment (M_DRIVE,FR, M_DRIVE,FL, M_DRIVE,RR, M_DRIVE,RL) previously built up additionally on a driven wheel (2, 3, 4, 5).
4. System for controlling vehicle-movement dynamics, which operates by means of the braking system and the drive train (6) of a vehicle (1) in order to prevent lateral breakaway of the vehicle (1), wherein a braking moment (M_BRAKE,FR) is produced, by means of the braking system, on the front wheel (3) on the outside of the bend, and an additional drive moment (M_DRIVE,FR, M_DPIVE,FL, M_DRIVE,RR, M_DRIVE,RL) is built up, by means of the drive train (6), on the driven wheels (2, 3, 4, 5), for the purpose of preventing oversteering of the vehicle (1), and wherein a higher-order or lower-order drive-slip control comes into action if the slip on one or more driven wheels (2, 3, 4, 5) exceeds a predetermined value due to the additionally built-up drive moment (M_DRIVE,FR, M_DRIVE,FL, M_DRIVE,RR, M_DRIVE,RL), characterized in that an additional braking moment (M_BRAKE,RR) is produced on the rear wheel (5) on the outside of the bend when the additional drive moment (M_DRIVE,RR, M_DRIVE,RL) is built up on the rear wheels (4, 5).
5. System according to claim 4, characterized in that the braking moment (M_BRAKE,RR) additionally produced on the rear wheel (5) on the outside of the bend is of an order of magnitude which is equal to that of the drive moment (M_DRIVE,RL) previously built up on the rear wheel (4) on the inside of the bend.
6. System according to claim 4 or 5, characterized in that the additional braking moment (M_BRAKE,RR) is produced on the rear wheel (5) on the outside of the bend only if the oversteer of the vehicle does not decrease after a predetermined period of time.
7. System according to any one of claims 4 to 6, characterized in that the additional braking moment (M_BRAKE,RR) is produced on the rear wheel (5) on the outside of the bend only if the drive moment (M_DRIVE,RR) produced on the rear wheel (5) on the outside of the bend has attained a predetermined value.

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